Coal and other material cargo made up of discrete parts and small particulate matter, such as iron or other metal ores, earth, gravel or sand, and other products are often transported in open top gondola cars coupled in an extended train of cars and pulled by a locomotive. Tippling systems or hopper chutes fill the gondola cars with the material being transported, and when they reach their destination systems unload the gondola cars, usually by rotating the cars to dump the material.
A problem that is encountered in transport of materials such as coal or ore that are made up of particles in the form of chunks of rock or smaller particles that break off during the mining of this material or extraction by other means, is that the gondola cars, when in movement, have a flow of air passing over them, sometimes at speeds of 50 or 60 mph or more. This produces wind on the top of the gondola cars that disturbs smaller particles in the discrete pieces of material being transported. The force of the wind is easily sufficient to lift smaller or even larger particles in the cargo load so they are carried out of the gondola car.
The particles that have been lifted out of the car fall to the ground, and this results in a large amount of material being left by the side of the railway tracks, especially near the initial loading area. In transport of coal, it has been determined that hundreds of pounds of coal may be lost every time a single gondola car is transported. This loss, multiplied by as many as one hundred gondola cars in a train, and that multiplied by many trains being used per day, means that a very large amount of material is simply lost in transport.
Some systems have been proposed for covering or enclosing the gondola cars, notably systems in which a lid is provided over the top of the gondola car. However, this complicates the operation when the gondola car is loaded, because usually a human operator must access the lid and open it when the gondola car is being loaded and then, after loading, the human operator must close this gondola car lid. This involves a substantial amount of labor which is undesirable, especially when it is considered how many gondola cars are normally involved in a train that is used to transport the particulate materials being discussed.
Similarly, use of another covering, such as a tarp or fabric covering over the top of the coal or other particulate material, requires a human operator to apply it, again complicating the loading operation.